CVE-2026-25927: OpenEMR Auth Bypass Vulnerability

CVE-2026-25927 Overview

OpenEMR is a free and open source electronic health records (EHR) and medical practice management application. A critical Insecure Direct Object Reference (IDOR) vulnerability exists in versions prior to 8.0.0 affecting the DICOM viewer state API. The vulnerability allows authenticated users to access and modify DICOM viewer states for documents they are not authorized to view by manipulating the doc_id parameter.

Critical Impact

Authenticated attackers can read or modify DICOM viewer state data (annotations, view settings) for any document in the system by enumerating document IDs, potentially exposing sensitive patient medical imaging data and allowing unauthorized modifications to medical records.

Affected Products

• OpenEMR versions prior to 8.0.0
• DICOM viewer state API endpoints (upload, state save/load)
• Healthcare installations using OpenEMR for DICOM image management

Discovery Timeline

• 2026-02-25 - CVE-2026-25927 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-25927

Vulnerability Analysis

This vulnerability is classified as CWE-639 (Authorization Bypass Through User-Controlled Key), commonly known as an Insecure Direct Object Reference (IDOR). The DICOM viewer state API in OpenEMR accepts a document ID (doc_id) parameter without performing adequate authorization checks to verify that the requested document belongs to a patient or encounter that the current user is authorized to access.

The flaw enables authenticated users to bypass horizontal access controls and interact with medical imaging data belonging to other patients. In a healthcare context, this represents a significant privacy violation as DICOM files contain sensitive diagnostic imaging data including X-rays, CT scans, MRIs, and associated annotations made by healthcare providers.

Root Cause

The root cause is a missing authorization check in the DICOM viewer state API. When processing requests for document operations such as uploading state data or saving/loading view settings, the application fails to validate whether the authenticated user has legitimate access to the specified doc_id. The API trusts the user-supplied document identifier without cross-referencing it against the user's authorized patient list or current encounter context.

Attack Vector

The attack is network-based and requires low-privilege authentication. An attacker with valid credentials to the OpenEMR system can exploit this vulnerability by manipulating the doc_id parameter in API requests to the DICOM viewer state endpoints.

The exploitation process involves:

1. An authenticated user identifies the DICOM viewer state API endpoints
2. The attacker enumerates document IDs by incrementing or predicting the doc_id parameter
3. For each valid document ID, the attacker can read existing DICOM viewer states (exposing annotations and view settings)
4. The attacker can also modify or overwrite DICOM viewer states for any document, potentially altering medical record annotations

This vulnerability requires no user interaction and can be exploited by any authenticated user with access to the DICOM viewer functionality. For more technical details, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-25927

Indicators of Compromise

• Unusual patterns of DICOM viewer state API requests with sequential or randomized doc_id values from a single user
• Access logs showing users requesting document IDs outside their assigned patient roster
• Unexpected modifications to DICOM viewer annotations or view settings
• High-volume API requests to DICOM state endpoints from individual user sessions

Detection Strategies

• Implement API request monitoring to detect enumeration patterns on the doc_id parameter
• Configure application logging to capture all DICOM viewer state API access attempts with user context
• Deploy Web Application Firewall (WAF) rules to detect rapid sequential parameter manipulation
• Cross-reference API access logs against user authorization records to identify unauthorized document access attempts

Monitoring Recommendations

• Enable verbose logging on DICOM viewer state API endpoints including user identity and document IDs accessed
• Implement alerting for users accessing documents outside their authorized patient encounters
• Monitor for anomalous spikes in DICOM viewer API traffic that may indicate enumeration attacks
• Conduct regular audits of DICOM viewer state access patterns to identify potential exploitation

How to Mitigate CVE-2026-25927

Immediate Actions Required

• Upgrade OpenEMR to version 8.0.0 or later immediately
• Audit access logs for any suspicious DICOM viewer state API activity prior to patching
• Review all DICOM viewer state data for unauthorized modifications
• Implement additional network segmentation to limit access to the OpenEMR application

Patch Information

OpenEMR version 8.0.0 includes the fix for this vulnerability. The patch implements proper authorization checks to verify that the requesting user has legitimate access to the document specified by the doc_id parameter before processing DICOM viewer state operations.

Organizations should upgrade to OpenEMR 8.0.0 as the primary remediation. For detailed patch information and release notes, refer to the GitHub Security Advisory.

Workarounds

• Restrict access to DICOM viewer functionality to only essential personnel until the patch can be applied
• Implement additional authentication layers or IP restrictions for accessing DICOM viewer state API endpoints
• Deploy a reverse proxy with authorization rules that validate document access permissions before forwarding requests
• Monitor and rate-limit API requests to DICOM viewer state endpoints to reduce enumeration effectiveness

# Example: Restrict access to DICOM viewer API at the web server level (Apache)
# Add to Apache configuration or .htaccess
<Location "/interface/modules/zend_modules/module/DicomViewer">
    Require ip 10.0.0.0/8
    Require ip 192.168.0.0/16
</Location>